<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    // function getSum(num1, num2) {
    //   console.log( num1 + num2 )
    // }

    // getSum(1, 2)
    // getSum(11, 12)

    function getSum(num1, num2) {
      var sum = 0

      for(var i = num1; i <= num2; i++) {
        sum += i
      }

      console.log( sum ) 
    }

    getSum(1, 2)
    getSum(10, 12)
  </script>
</body>
</html>